Certain plants represent sustainable sources of natural rubber. Natural rubber can be extracted from such plants for use industry, for example, in the tire, medical and consumer products industries. One plant, guayule, is a perennial shrub that is a renewable source of natural rubber. The natural rubber extracted from guayule, which is native to Southwestern U.S., can replace petroleum-based synthetics and reduce reliance on imported natural rubber. The guayule is desirable because it advantageously requires relatively low amounts of water and pesticides, which reduces the costs of raising and harvesting this sustainable source of natural rubber. Another plant, the hevea tree, is also a renewable source of natural rubber. The hevea tree represents the primary source of natural rubber used in tire production.
Breeding and harvesting methods for rubber-bearing plants focus on maximizing the amount of available extractable rubber. Rapid screening methods for estimating the amount of natural rubber in harvestable plants has proven difficult. For example, guayule, which has rubber throughout its plant tissues, often requires time intensive methods, such as solvent extraction and lengthy sample preparation, for estimating extractable rubber content. Sample preparation, extraction methods and long analysis times can substantially limit the number of analyses which can be completed each day. Further, methods based on the use of high resolution or high-field NMR spectrums require expensive and large equipment having strong magnets and cumbersome probe electronics that are not readily transportable to the field. Analysis time using high resolution NMR apparatuses is lengthy and thus such use is not suitable for rapid screening of plants, either in the lab or field. There remains a need for more robust and accurate methods for quantifying natural rubber in a plant, and further for rapid, field-ready methods for accurately quantifying the amount of natural rubber in plants that reduces the costs and lengthy analysis time associated with more sensitive laboratory equipment.